1. Field of the Invention
The present invention relates to a charging member, a process cartridge, and an electrophotographic apparatus.
2. Description of the Related Art
The following construction has been generally adopted for a contact-type charging member in an electrophotographic apparatus. The charging member has an elastic layer for securing a nip width. A problem of such charging member is a compression set (hereinafter, referred to as “C set”) that occurs when the charging member is left to stand in a state of being brought into abutment with an electrophotographic photosensitive member over a long time period. The C set becomes more remarkable as the temperature and humidity of the environment under which the charging member is left to stand become higher. In the case where the electrophotographic photosensitive member is charged with the charging member in which the C set has occurred, a uniform micro-discharge gap cannot be maintained when a portion where the C set is occurring (hereinafter, referred to as “C set portion”) passes a discharge region.
Thus, there arises a difference in the charging ability of the charging member between the C set portion and a non-C set portion. As a result, streak-like unevenness may occur at the position of an electrophotographic image corresponding to the C set portion of the charging member. The unevenness is apt to occur in such image particularly when only a DC voltage is used as a voltage to be applied to the charging member. Japanese Patent Application Laid-Open No. H09-244348 and Japanese Patent Application Laid-Open No. H08-69148 each disclose an invention relating to the alleviation of such C set.